In railroad and/or mass and rapid transit operations, it is common practice to employ an event monitoring and recording system for providing at any particular time an authentic and actual record of a given number of different occurrences that take place over an extended period of time during the course of travel of the train. In many cases, it is advantageous to provide a tangible and accurate record of each event as well as the time, day and location at which the particular individual event occurs. That is, there is a need and demand to monitor a large number of parameters or operating conditions, such as, pneumatic brake application and release, dynamic brakes, throttle setting, speed, distance traveled, time, brake pipe pressure reduction, fuel consumption, sanding, as well as warning horn actuation for immediate and subsequent evaluation. In particular, when used on a locomotive and transit car, it is immensely valuable to monitor and record the given speed and the actual sounding of the warning horn at a certain track location, such as a highway-railroad crossing, at a common grade, for subsequent review and use in case of an accident. In the past, it was the word of the engineer against that of the victim as to whether the warning device was actuated and actually sounded prior to the time of the accident. However, it is well known that air horns have a threshold level of operating pressure below which the emitted sound drops off rapidly or ceases entirely. In normal operation, the air horn has a sound level of 106 to 112 decibels (DB) at pressures of 70 to 140 psi, and has an audible range of between 5 to 5.5 miles. However, in the past there was no positive way of determining whether the operator of the train had actually operated the air horn valve and whether the air pressure of the main reservoir was above the threshold level at the time the air horn valve was actuated. It would be highly advantageous and very helpful in liability lawsuits to unequivocally provide absolute and irrefutable proof that the warning horn or bell was in fact sounded as the train approached the highway grade crossing before the occurrence of the accident. In addition, the actuation of the whistle valve and sounding of the horn could be very useful in determining and checking the alertness of the locomotive engineer or trainman which requires him to establish his vigilance and awareness as the train moves along its route of travel. For example, the operation of the air horn could be used as a signal for signifying the alertness of the operator as well as being recorded in an event recording apparatus.